calculation-of-sun/dist/solar-calculation.js

class Sunpositioning {
  /* Earth */
  /* J0: 0.0009
     J1: 0.0053
     J2: -0.0068
     J3: 1 */

     /*
   	             h0	    dSun	 sin(h0)
      Mercury 	−0.69 	1.38 	−0.0120
      Venus 	−0.37 	0.74 	−0.0064
      Earth 	−0.83 	0.53 	−0.0146
      Mars 	    −0.17 	0.35 	−0.0031
    */
    /*
         	           M0           M1
        Mercury 	174.7948 	4.09233445
        Venus 	    50.4161 	1.60213034
        Earth 	    357.5291 	0.98560028
        Mars 	    19.3730 	0.52402068
        Jupiter 	20.0202 	0.08308529
        Saturn 	    317.0207 	0.03344414
        Uranus 	    141.0498 	0.01172834
        Neptune 	256.2250 	0.00598103
        Pluto 	    14.882 	    0.00396
    */
    constructor(){
        this.JD1970 = 2440588;
        this.JD2000 = 2451545;
        this.earthC_coefficient_component = {
            C1: 1.9148,
            C2: 0.0200,
            C3: 0.0003,
            C4: 0,
            C5: 0,
            C6: 0,
            EC: 0.0000
        };
        this.earth_perihelion = 102.94719;
        this.earth_obliquity = 23.44 * (Math.PI / 180);
        this.earth_obliquity_degrees = 23.44;
        this.earth_sideral_time = {
            at_zero_long: 280.1470,
            rate_of_change: 360.9856235
        };

    }

    getSunInformation(date, lat, long) {
        this.CLIENT_JD = this.dateToJD(date);
        this.CLIENT_LATITUDE = lat;
        this.CLIENT_LONGTITUDE = long;
        this.CLIENT_lw = -long;
        let position = this.getSunPosition();
        return {
            sun_position: {
                azimuth: position.azimuth.degrees,
                altitude: position.altitude.degrees
            },
            date: this.jdToDate(this.CLIENT_JD).toString(),
            sunrise: this.jdToDate(this.sunriseandsunset(this.CLIENT_JD).sunrise).toString(),
            sunset: this.jdToDate(this.sunriseandsunset(this.CLIENT_JD).sunset).toString(),
            mean_anomaly: this.earthMeanAnomaly(this.CLIENT_JD),
            solar_transit: this.solarTransit(this.CLIENT_JD),
            equation_of_center: this.equation_of_center(this.CLIENT_JD),
            h: this.getHourAngle(this.CLIENT_JD),
            RA: this.rightAscension(this.CLIENT_JD),
            clientJD: this.CLIENT_JD,
            true_anomaly: this.earthTrueAnomaly(this.CLIENT_JD),
            sideraltime: this.sideraltime(this.CLIENT_JD)
        };
    }

    dateToJD(date) {
        return date.valueOf() / ( 1000 * 60 * 60 * 24 ) - 0.5 + this.JD1970;
    }

    jdToDate(jd) {
        return new Date((jd + 0.5 - this.JD1970) * ( 1000 * 60 * 60 * 24 ) )
    }

    equation_of_center(jd) {
        /*
            the C4 - C6 are 0, so I just calculate for Coefficient 1 - 3.
        */
        let results = this.earthC_coefficient_component.C1 * Math.sin(this.earthMeanAnomaly(jd).rad) + 
                        this.earthC_coefficient_component.C2 * Math.sin(2 * this.earthMeanAnomaly(jd).rad) + 
                        this.earthC_coefficient_component.C3 * Math.sin(3 * this.earthMeanAnomaly(jd).rad);
        return {
            degrees: results,
            rad: results * (Math.PI / 180)
        };
    }

    earthMeanAnomaly(jd) {
        return {
            degrees: ( 357.5291 + 0.98560028 * ( jd - this.JD2000 ) ) % 360,
            rad: (( 357.5291 + 0.98560028 * ( jd - this.JD2000 ) ) % 360) * (Math.PI / 180)
        }
    }

    earthTrueAnomaly(jd) {
        let results = this.equation_of_center(jd).degrees + this.earthMeanAnomaly(jd).degrees;
        return {
            degrees: results,
            rad: results * (Math.PI / 180)
        }
    }

    eclipticLongtitude(jd) {
        let true_anomaly = this.earthTrueAnomaly(jd);
        let results = (true_anomaly.degrees + this.earth_perihelion + 180) % 360;
        return {
            degrees: results,
            rad: results * (Math.PI / 180)
        };
    }

    rightAscension(jd) {
        let ecliptic_longtitude = this.eclipticLongtitude(jd);
        let results = Math.atan2(Math.sin(ecliptic_longtitude.rad) * Math.cos(this.earth_obliquity), Math.cos(ecliptic_longtitude.rad));
        return {
            degrees: results / (Math.PI / 180),
            rad: results
        };
    }

    declination(jd) {
        let ecliptic_longtitude = this.eclipticLongtitude(jd);
        let results = Math.asin(Math.sin(ecliptic_longtitude.rad) * Math.sin(this.earth_obliquity));
        return {
            degrees: results / (Math.PI / 180),
            rad: results
        };
    }

    sideraltime(jd) {
        let results = (this.earth_sideral_time.at_zero_long + this.earth_sideral_time.rate_of_change * (jd - this.JD2000) - (this.CLIENT_lw)) % 360;
        return results;
    }

    getHourAngle(jd) {
        return this.sideraltime(jd) - this.rightAscension(jd).degrees;
    }

    getSunPosition() {
        return {
            azimuth: {
                rad: Math.atan2(Math.sin(this.getHourAngle(this.CLIENT_JD) * Math.PI / 180), 
                Math.cos(this.getHourAngle(this.CLIENT_JD) * Math.PI / 180) * Math.sin(this.CLIENT_LATITUDE * Math.PI / 180) - Math.tan(this.declination(this.CLIENT_JD).rad) * Math.cos(this.CLIENT_LATITUDE * Math.PI / 180)),
                degrees: Math.atan2(Math.sin(this.getHourAngle(this.CLIENT_JD) * Math.PI / 180), 
                Math.cos(this.getHourAngle(this.CLIENT_JD) * Math.PI / 180) * Math.sin(this.CLIENT_LATITUDE * Math.PI / 180) - 
            Math.tan(this.declination(this.CLIENT_JD).rad) * Math.cos(this.CLIENT_LATITUDE * Math.PI / 180)) / (Math.PI / 180)
            },
            altitude: {
                rad: Math.asin(Math.sin(this.CLIENT_LATITUDE * (Math.PI / 180)) * Math.sin(this.declination(this.CLIENT_JD).rad) + 
                Math.cos(this.CLIENT_LATITUDE * Math.PI / 180) * Math.cos(this.declination(this.CLIENT_JD).rad) * Math.cos(this.getHourAngle(this.CLIENT_JD) * Math.PI / 180)),
                degrees: Math.asin(Math.sin(this.CLIENT_LATITUDE * (Math.PI / 180)) * Math.sin(this.declination(this.CLIENT_JD).rad) + 
                Math.cos(this.CLIENT_LATITUDE * Math.PI / 180) * Math.cos(this.declination(this.CLIENT_JD).rad) * Math.cos(this.getHourAngle(this.CLIENT_JD) * Math.PI / 180)) / (Math.PI / 180)
            }
        }
    }

    solarTransit(jd) {
        let lw = this.CLIENT_lw;
        let _JD2000 = this.JD2000
        function nx() { return ((jd - _JD2000 - 0.0009) / 1 - (lw / 360)); }
        let n = Math.round(nx());
        function JDX() { return jd + 1 * ( n - nx() ); }
        let M = this.earthMeanAnomaly(JDX()).degrees;
        let L = (M + this.earth_perihelion + 180) % 360;
        let JDtmp = JDX() + 0.0053 * Math.sin(M * Math.PI / 180) - 0.0068 * Math.sin(2 * (L * (Math.PI / 180)));
        return JDtmp - (0 / 360 ) * 1;
    }

    sunriseandsunset(jd) {
        let jd_from_approx_transit = this.solarTransit(jd);
        let sundeclination = this.declination(jd_from_approx_transit);
        let Ht = Math.acos((-0.0146 - Math.sin(this.CLIENT_LATITUDE * Math.PI / 180) * Math.sin(sundeclination.rad)) / 
                    Math.cos(this.CLIENT_LATITUDE * Math.PI / 180) * Math.cos(sundeclination.rad));
        return {
            sunrise: jd_from_approx_transit - ((Ht / (Math.PI / 180)) / 360) * 1,
            sunset: jd_from_approx_transit + ((Ht / (Math.PI / 180)) / 360) * 1
        }
    }
}

module.exports = Sunpositioning;